The invention in general relates to a novel method of false twist texturing a yarn and, more particularly, to such a method providing for control of the tension imparted to the advancing yarn.
U.S. Pat. No. 5,146,739 to Lorenz discloses a yarn false twist texturing process and apparatus which includes monitoring the tension of an advancing yarn and processing the monitored tension signal to derive an adjusting signal which acts to control the false twisting unit in a manner providing a substantially constant tension. The process and apparatus disclosed in the Lorenz Patent are functioning satisfactorily in normal operations with the yarn having reached desired speed and temperature. However, the process and apparatus are not suited to funtion properly in non-normal operations as, for instance, during yarn thread-up operations, or when the machine decelerates because of temporary power failures or the like.
Except as otherwise noted herein, the yarn thread-up operation or procedure includes the steps of threading an advancing yarn into a first feed system, a heated plate, a cooling plate, and a false twist unit. It may also extend in the subsequent operating period in which the yarn has not yet reached its desired operating conditions.
Temporary electrical power failures occur relatively frequently; desirably, they should not, however, result in any broken yarns, since that would necessitate re-threading all of those yarns in the texturing machine. This would be particularly disconcerting in cases where such re-threading is carried out by automatic equipment, such as a doffer, movable along the front of the machine.
Accordingly, it is an object of the present invention to provide for a process and apparatus for controlling a false twist texturing machine by effectively controlling the operating parameters during periods of normal operation as well as during periods of other than normal operation, as, for instance, during yarn thread-up operations or during decelerations of the machine induced by temporary power failures.
It is more particular object of the present invention to provide for a process and apparatus of the kind referred to which better adapts the texturing machine to servicing by an automatic doffer.